Sn4+, In3+ are relatively strong Lewis acids respect Zn2+ and Mg2+ and these ions are in equilibrium with Br- (e.g. provided by tetrabuthylamminium bromide TBAB).

In literature I have found that in water, in excess of Br-, In3+ is coordinated with 3,4,5 up to 6 Br- forming the anionic species of TBA+ (e.g.).

Is this happening also for Sn4+? (I guess yes because of high acidity).

More interesting, I still struggle in this following case: what happens with Zn2+ and Mg2+? Are they only coordinated with 2 Br- forming the neutrale species (+ cooridnated solvent molecules) or with more Br-? May someone provide me some citations with equilibrium constants?

I'm using principally MeOH, ACN as solvents. In case of DMSO an DMF as solvents, what happens when Mg2+ is present in excess of Br-?

Thanks in advance for your time!

Daniel T.